Re: [PATCH v1 2/2] scsi: ufs: core: Reduce the sleep before vcc can be powered on

[Bao D. Nguyen]

On 10/2/2025 8:11 PM, Peter Wang (王信友) wrote:
> On Thu, 2025-10-02 at 12:00 -0700, Bao D. Nguyen wrote:
> > Hi Peter,
> > I have discussed with the major ufs vendors (Samsung, Kioxia, Micron,
> > and SK Hynix) via emails. They are all in agreement that 2ms is good.
> > I
> > did check the current device's datasheets and 1ms is what their
> > specifications require. I admit that I may have missed some very old
> > ufs
> > device's datasheets. However, I take the words of the ufs vendor's
> > engineering teams and the current device's datasheets that the 2ms is
> > good for their devices and try to improve the potentially
> > conservative
> > 5ms delay parameter.
> >
> > Thanks, Bao
>
> Hi Bao,
>
> Yes, I am concerned that legacy UFS devices may encounter errors
> when upgrading the kernel if the delay is not sufficient.
>
> Furthermore, the vendor claims that 2ms is sufficient. Is this
> based on a typical scenario? or should we be concerned about
> the worst-case scenario? I am also worried that the worst-case
> delay may not be enough.

With the current or recent offerings of ufs devices in the market, the 
requirement is 1ms. For example, the Kioxia datasheet says "Vcc shall be 
kept less than 0.3V for at least 1ms before it goes beyond 0.3V again". 
Similarly other vendors have this 1ms requirement. So I believe this 
indicates the worst case scenario.
I understand there may be very old devices that are upgrading the kernel 
only. In that case I don't know the specifics for these old ufs parts as 
mentioned.

Thanks, Bao

> Thanks
> Peter